1. Field of the Invention
The invention relates to a steering column module having modular functional units and an associated electrical unit.
2. Background Art
Such steering columns are provided in motor vehicles for the purpose of initiating and executing various functions, e.g., direction indication and wiper-washer operations, signal transmission, and steering angle acquisition.
In a conventional structure, the various functional units are designed as separate electronic or electromechanical modules which are arranged in different axial planes along the steering axis. The modules may also concentrically wrap around the steering column.
The functional units can encompass, for example, a coil spring cassette for power supply and signal transmission in the steering wheel, a steering angle sensor for acquiring the steering angle, and different steering column switching components. Such functional units are allocated to the varying operating functions, e.g., direction indication, windshield washing function, etc.
An electronics unit is allocated to the different functional units. The electronics unit contains a printed circuit board which carries the power, the evaluation, and, if necessary, the control electronics of the functional units, and connects the different functional units with the onboard power supply system. Detachable plug-in connectors are provided for contacting the different functional units with the electronics unit.
In a previously known configuration, e.g., as known from EP 0 853 022 A1, the electronics unit forms its own plane in the structure of the steering column module, and is hence integrated into the layered structure of the steering column module. In this previously known configuration, the electronics unit forms a lowermost plane on which several steering column assembly switches forming a functional unit are arranged in a first overlying plane. The side-by-side arrangement makes it easy to establish direct contact between the switches and electronics.
A functional unit such as a coil spring cassette is situated in another plane above the plane of the steering column assembly switch. In order for it to also be connected with the electronics unit, it has a longitudinal projection extending through the arrangement of steering column assembly switches and into the plane of the electronics unit such that it can be introduced into a plug-in connector part located therein.
While several functional units can be arranged in this previously known steering column module and electrically contacted in various planes, the functional units not directly adjacent to the electronics module must be extended through the other ones.
Therefore, this layered layout of functional units results in printed conductors of varying length to the different modules. In particular, in steering column modules containing many functional layers, the functional unit located the farthest away from the electronics unit is connected to the electronics unit by comparatively long contact tabs. In functional units where signals that are very low relative to their voltage or current level transmitted, e.g., in the case of a steering angle sensor, electromagnetic interference can trigger disturbances in the printed conductors and thereby impair the functional reliability of the unit.
The operational reliability of the functional units contacted by plug-in connectors can also be negatively impacted, in particular after many years of operation and under unfavorable environmental conditions, e.g., a high level of atmospheric humidity in the environment, for example by an oxidation of the contacts. This makes it necessary to use especially high quality, e.g., gold-plated and/or specially encapsulated plug-in contacts, but these are very cost-intensive.
Therefore, an object of the present invention is to provide a steering column module that avoids long connection paths for susceptible electronic functional units, exhibits a high operational reliability and a compact modular structure, and is cost-effective in realization.
This object is achieved according to the present invention by the features specified in the characterizing clause of the main claim.
In such a structure, it is especially advantageous to combine the advantages of a modular structure for the steering column module, relative to the flexibility and ease of maintenance of the individual components, with the advantages from integrating sensitive functional units into assemblies.
In the steering column module according to the present invention, a sensitive functional unit is integrated with the electronics unit in a shared casing into an inseparable, compact assembly. Preferably, a permanent electrical connection exists between the electronics and functional units.
The permanent connection can be established using directly soldered cables, but the electronic components of the functional unit and the components of the electronics unit cooperating therewith are preferably situated on a shared, non-conductive substrate provided with electrical printed conductors. The substrate can be a printed circuit board or a flexible film.
Preferably, the functional unit integrated into the assembly is a steering angle sensor, wherein the latter is situated transverse to the steering axis and at least partially wraps around it, and wherein the integrated electronics unit is preferably situated parallel to the steering axis. This type of arrangement results in an essentially angled, L-shaped structure. The substrate carrying the printed conductors is here also angled.
If the substrate is designed as a printed circuit board, the angled configuration of the printed circuit board can be achieved by diminishing the printed circuit board on the side facing away from the printed conductors to a thickness of typically several tenths of a millimeter. This can be done through mechanical sinking so that the printed circuit board can be flipped over without breaking the board material.
In an alternative embodiment, the substrate is designed as a flexible film which can be angled without any problem. The printed conductor film is here preferably abutted against a supporting structure inside the casing which is secured in the two arms of the L-shaped structure.
In another embodiment, plug-in connector parts pointing in the radial or tangential direction are secured on the arms of the L-shaped angled structure that accommodate the electronics unit, on the side facing the steering axis relative to the plugging direction, so that additional functional units can be hooked up to these arms over a short path via the corresponding plug-in connector parts. Additional functional units, e.g., ones that are less sensitive, can also be hooked up via longer line paths with an axial plug-in direction, if necessary.
In another embodiment of the steering column module, a second sensitive functional unit is combined with the electronics unit and the first functional unit to form an inseparable, essentially U-shaped assembly. The middle part of the U-shaped assembly is situated parallel to the steering axis and has plug-in connector parts extending in a radial and tangential direction. The second functional unit can be a torque sensor, for example. In this configuration as well, the electronics unit is directly and undetachably connected with the first and second functional unit via lines such as conductors, wherein the lines are preferably placed on a shared substrate that is angled in the shape of a U and extends into all parts of the U-shaped casing. The arms of the assembly allocated to the integrated functional units can here at least partially wrap around the steering column.